AD 2008-09-16

This AD becomes effective June 6, 2008.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of June 6, 2008.

You may examine the AD docket on the Internet at http://www.regulations.gov or in person at the U.S. Department of Transportation, Docket Operations, M-30, West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC.

Tim Dulin, Aerospace Engineer, International Branch, ANM-116, Transport Airplane Directorate, FAA, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 227-2141; fax (425) 227-1149.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to the specified products. That NPRM was published in the Federal Register on October 25, 2007 (72 FR 60591). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:

A number of occurrences of an incorrect installation of the trimmable horizontal stabilizer actuator (THSA) have been found and reported during the accomplishment of the AIRBUS Service Bulletin (SB) A320-27-1164 mandated by EASA AD 2006-0223.

These issues could lead to a degradation of the integrity of the THSA primary load path and to secondary load path partial or full engagement. This AD therefore mandates a one-time detailed visual inspection of specific parts of the THSA attachments.

Degradation of the THSA primary load path could result in latent (undetected) loading and eventual failure of the THSA secondary load path, with consequent uncontrolled movement of the horizontal stabilizer and loss of control of the airplane. The corrective actions include doing a one-time detailed visual inspection of the lower and the upper THSA attachments for correct installation and the presence of metallic particles, contacting Airbus for repair instructions if any installation deviations or metallic particles are found, and doing repairs. You may obtain further information by examining the MCAI in the AD docket.

We gave the public the opportunity to participate in developing this AD. We considered the comment received.

The Air Transport Association (ATA), on behalf of its member Northwest Airlines (NWA), requests that we reconsider the need for this proposed AD. NWA states that the proposed rule is based on reports from Airbus of a number of occurrences of incorrect THSA installations that resulted from published procedures not being followed either during aircraft production or by operators after delivery of the aircraft. NWA agrees that an incorrectly installed THSA could be a safety concern, but asserts that accomplishing a one-time inspection will not prevent improper THSA installations in the future, and does not understand what corrective action is being taken (or should be taken) to prevent similar installation problems in the future. Furthermore, NWA feels that the airplane maintenance manual (AMM) is clear and concise regarding THSA installation procedures and states that, unless incorrect installations were accomplished during production or the AMM installation instructions were incorrect, a one-time inspection mandated by an AD is unwarranted. NWA asserts that it has accomplished AD 2007-06-02, amendment 39-14983 (72 FR 12072, March 15, 2007), on all its Model A319 and A320 airplanes with no findings of note. (AD 2007-06-02, which corresponds to EASA AD 2006-0223, dated July 21, 2006, requires inspections of the upper and lower THSA attachments for proper clearances, and for the presence of cracking, damage, and metallic particles.) NWA concludes that incorrect installations due to operator error should be addressed by actions other than issuing an all-fleet AD.

Although we understand NWA's concern, we do not agree with this request. If incorrect THSA installation was limited to only one operator (an isolated case of not following maintenance instructions), an AD would not have been an appropriate method of dealing with the situation. However, as THSA installation errors have been reported at multiple operators, and installation errors could result in the identified unsafe condition that is likely to exist or develop on other airplanes, an AD is appropriate. Further, we have determined that, although technically correct, the maintenance instructions were insufficiently clear to ensure that no confusion could occur during installation of the THSA. In regard to future installations, Airbus has informed us that the maintenance instructions have been revised and clarified to prevent confusion during any future installation of the THSA. We have not changed the AD in this regard.

We reviewed the available data, including the comment received, and determined that air safety and the public interest require adopting the AD as proposed.

We have reviewed the MCAI and related service information and, in general, agree with their substance. But we might have found it necessary to use different words from those in the MCAI to ensure the AD is clear for U.S. operators and is enforceable. In making these changes, we do not intend to differ substantively from the information provided in the MCAI and related service information.

We might also have required different actions in this AD from those in the MCAI in order to follow our FAA policies. Any such differences are highlighted in a NOTE within the AD.

We estimate that this AD will affect 721 products of U.S. registry. We also estimate that it will take about 3 work-hours per product to comply with the basic requirements of this AD. The average labor rate is $80 per work-hour. Based on these figures, we estimate the cost of this AD to the U.S. operators to be $173,040, or $240 per product.

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. “Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

We determined that this AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this AD:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and

3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket.

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains the NPRM, the regulatory evaluation, any comments received, and other information. The street address for the Docket Operations office (telephone (800) 647-5527) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new AD: